Performance of hydro-acoustic data transmission in horizontal channels using sweep-spread signaling and turbo-coding

Abstract

Using the sweep-spread carrier it can be demonstrated that in result of optimal filtering of dominated (synchronous) multipath all other (non-synchronous) multipahts become attenuated. This causes an increase of the ratio between the energy of synchronous multipath component and scattered energy of non-synchronous multipaths. Thus the probability distributions of signal envelope and phase become closer to Gaussian one. So the use of the sweep-spread carrier in hydroacoustic channels allows for application of turbo-codes, what, in turn, leads to increase of reliability of data transmission under condition of low ratios between signal energy and the energy of ambient noise (few decibels). The paper characterizes performance of a receiver combining the optimal quadrature demodulator and turbo-decoder.

Modelling and validation of basic characteristics in underwater acoustic sweep-spread-carrier communications

“…6 shows the superposition of several of multipath intensity profiles recorded in the test on data transmission over the distance of 328 m. Their comparison with multipath intensity profile obtained by the simulations (Fig. 4) shows their similarity, both in terms of the number of multipath arrivals (3)(4) and the their excess propagation delays (about 4 ms). The difference consists in their levels (differences between arrivals expected to be larger when simulating their propagation), as well as in dynamics of the arrivals (when simulating their propagation the dynamics expected to be less).…”